Exception in acme.get_certificate() causes package to crash without cleanup

[nsmcan]

It works fine since January 2019. Recently got an SSL exception in acme.get_certificate(). As a result, script crashed and didn't remove temporary nginx site config 0-letsencrypt.conf. Website functionality was affected.

P.S. I have updated your package to work in Windows, will submit pull request soon...

2019-10-08 01:00:09,103 - INFO - writing challenge file into C:/Tools/nginx/conf/sites-enabled/0-letsencrypt.conf
2019-10-08 01:00:09,103 - INFO - asking acme server to verify challenge
Traceback (most recent call last):
  File "c:\tools\python36-32\lib\urllib\request.py", line 1318, in do_open
    encode_chunked=req.has_header('Transfer-encoding'))
  File "c:\tools\python36-32\lib\http\client.py", line 1239, in request
    self._send_request(method, url, body, headers, encode_chunked)
  File "c:\tools\python36-32\lib\http\client.py", line 1285, in _send_request
    self.endheaders(body, encode_chunked=encode_chunked)
  File "c:\tools\python36-32\lib\http\client.py", line 1234, in endheaders
    self._send_output(message_body, encode_chunked=encode_chunked)
  File "c:\tools\python36-32\lib\http\client.py", line 1026, in _send_output
    self.send(msg)
  File "c:\tools\python36-32\lib\http\client.py", line 964, in send
    self.connect()
  File "c:\tools\python36-32\lib\http\client.py", line 1400, in connect
    server_hostname=server_hostname)
  File "c:\tools\python36-32\lib\ssl.py", line 407, in wrap_socket
    _context=self, _session=session)
  File "c:\tools\python36-32\lib\ssl.py", line 817, in __init__
    self.do_handshake()
  File "c:\tools\python36-32\lib\ssl.py", line 1077, in do_handshake
    self._sslobj.do_handshake()
  File "c:\tools\python36-32\lib\ssl.py", line 689, in do_handshake
    self._sslobj.do_handshake()
ssl.SSLEOFError: EOF occurred in violation of protocol (_ssl.c:852)

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "c:\tools\python36-32\lib\runpy.py", line 193, in _run_module_as_main
    "__main__", mod_spec)
  File "c:\tools\python36-32\lib\runpy.py", line 85, in _run_code
    exec(code, run_globals)
  File "C:\Tools\Python36-32\Scripts\acme-nginx.exe\__main__.py", line 9, in <module>
  File "c:\tools\python36-32\lib\site-packages\acme_nginx\client.py", line 121, in main
    acme.get_certificate()
  File "c:\tools\python36-32\lib\site-packages\acme_nginx\AcmeV2.py", line 194, in get_certificate
    self.solve_http_challenge(directory)
  File "c:\tools\python36-32\lib\site-packages\acme_nginx\AcmeV2.py", line 114, in solve_http_challenge
    code, result, _ = self._send_signed_request(url=challenge['url'], directory=directory)
  File "c:\tools\python36-32\lib\site-packages\acme_nginx\Acme.py", line 248, in _send_signed_request
    headers=request_headers)
  File "c:\tools\python36-32\lib\urllib\request.py", line 223, in urlopen
    return opener.open(url, data, timeout)
  File "c:\tools\python36-32\lib\urllib\request.py", line 526, in open
    response = self._open(req, data)
  File "c:\tools\python36-32\lib\urllib\request.py", line 544, in _open
    '_open', req)
  File "c:\tools\python36-32\lib\urllib\request.py", line 504, in _call_chain
    result = func(*args)
  File "c:\tools\python36-32\lib\urllib\request.py", line 1361, in https_open
    context=self._context, check_hostname=self._check_hostname)
  File "c:\tools\python36-32\lib\urllib\request.py", line 1320, in do_open
    raise URLError(err)
urllib.error.URLError: <urlopen error EOF occurred in violation of protocol (_ssl.c:852)>